TY - CONF AU - Suess, Tim AU - Schoenrock, Andrew AU - Meisner, Sebastian AU - Plessl, Christian ID - 1787 SN - 978-0-7695-4979-8 T2 - Proc. Int. Symp. on Parallel and Distributed Processing Workshops (IPDPSW) TI - Parallel Macro Pipelining on the Intel SCC Many-Core Computer ER - TY - CONF AB - This paper investigates the properties required to evolve Artificial Neural Networks for distributed control in modular robotics, which typically involves non-linear dynamics and complex interactions in the sensori-motor space. We investigate the relation between macro-scale properties (such as modularity and regularity) and micro-scale properties in Neural Network controllers. We show how neurons capable of multiplicative-like arithmetic operations may increase the performance of controllers in several ways whenever challenging control problems with non-linear dynamics are involved. This paper provides evidence that performance and robustness of evolved controllers can be improved by a combination of carefully chosen micro- and macro-scale neural network properties. AU - Hamann, Heiko AU - Stradner, Jürgen AU - Bredeche, Nicolas AU - Cazenille, Leo ID - 20173 T2 - 14th Annual Genetic and Evolutionary Computation Conference, GECCO 2012 TI - Impact of Neuron Models and Network Structure on Evolving Modular Robot Neural Network Controllers ER - TY - CONF AB - As a contribution to the efforts towards robotic systems of higher flexibility we present our concept of morphologically dynamic robots. Within the projects SYMBRION and REPLICATOR, that focus on modular robotics, we have developed bio-inspired control techniques to achieve new concepts of dynamic, autonomous morphological structures. We propose three modes of coupling between robot modules: swarm, team, and organism mode. We demonstrate our concepts along with simple robot experiments. AU - Hamann, Heiko AU - Schmickl, Thomas AU - Stradner, Jürgen ID - 20174 T2 - Austrian Robotics Workshop (Operational Programme Slovenia-Austria) TI - Towards Morphological Flexibility: Modular Robotics and Bio-inspired Control ER - TY - CONF AU - Hamann, Heiko AU - Schmickl, Thomas AU - Stradner, Jürgen AU - Crailsheim, Karl AU - Zahadat, Payam AU - Adami, Christoph AU - Bryson, David M. AU - Ofria, Charles AU - Pennock, Robert T. ID - 20175 T2 - Alife XIII TI - On-line, On-board Evolution of Reaction-Diffusion Control for Self-Adaptation ER - TY - JOUR AU - Hamann, Heiko AU - Schmickl, Thomas AU - Crailsheim, Karl ID - 20176 IS - 1 JF - Mathematical and Computer Modelling of Dynamical Systems SN - 1387-3954 TI - Self-organized pattern formation in a swarm system as a transient phenomenon of non-linear dynamics VL - 18 ER - TY - JOUR AB - One of the main challenges in automatic controller synthesis is to develop methods that can successfully be applied for complex tasks. The difficulty is increased even more in the case of settings with multiple interacting agents. We apply the artificial homeostatic hormone system (AHHS) approach, which is inspired by the signaling network of unicellular organisms, to control a system of several independently acting agents decentrally. The approach is designed for evaluation-minimal, artificial evolution in order to be applicable to complex modular robotics scenarios. The performance of AHHS controllers is compared with neuroevolution of augmenting topologies (NEAT) in the coupled inverted pendulums benchmark. AHHS controllers are found to be better for multimodular settings. We analyze the evolved controllers with regard to the usage of sensory inputs and the emerging oscillations, and we give a nonlinear dynamics interpretation. The generalization of evolved controllers to initial conditions far from the original conditions is investigated and found to be good. Similarly, the performance of controllers scales well even with module numbers different from the original domain the controller was evolved for. Two reference implementations of a similar controller approach are reported and shown to have shortcomings. We discuss the related work and conclude by summarizing the main contributions of our work. AU - Hamann, Heiko AU - Schmickl, Thomas AU - Crailsheim, Karl ID - 20177 IS - 2 JF - Artificial Life SN - 1064-5462 TI - A Hormone-Based Controller for Evaluation-Minimal Evolution in Decentrally Controlled Systems VL - 18 ER - TY - JOUR AU - Hamann, Heiko AU - Schmickl, Thomas AU - Wörn, Heinz AU - Crailsheim, Karl ID - 20178 IS - 2 JF - Neural Computing and Applications SN - 0941-0643 TI - Analysis of emergent symmetry breaking in collective decision making VL - 21 ER - TY - CONF AU - Hamann, Heiko AU - Engelbrecht, Andreas AU - Birattari, Mauro AU - Dorigo, Marco AU - Blum, Christian AU - Stuetzle, Thomas AU - Christensen, Anders Lyhne AU - Gross, Roderich ID - 20179 SN - 0302-9743 T2 - Swarm Intelligence: 8th International Conference, ANTS 2012 TI - Towards Swarm Calculus: Universal Properties of Swarm Performance and Collective Decisions VL - 7461 ER - TY - CONF AU - Cohen, Reuven AU - Nudelman, Ilia AU - Polevoy, Gleb ID - 17664 T2 - Infocom'2012, Orlando, Florida TI - On the Admission of Dependent Flows in Powerful Sensor Networks ER - TY - JOUR AB - A left-to-right maximum in a sequence of n numbers s_1, …, s_n is a number that is strictly larger than all preceding numbers. In this article we present a smoothed analysis of the number of left-to-right maxima in the presence of additive random noise. We show that for every sequence of n numbers s_i ∈ [0,1] that are perturbed by uniform noise from the interval [-ε,ε], the expected number of left-to-right maxima is Θ(&sqrt;n/ε + log n) for ε>1/n. For Gaussian noise with standard deviation σ we obtain a bound of O((log3/2 n)/σ + log n).We apply our results to the analysis of the smoothed height of binary search trees and the smoothed number of comparisons in the quicksort algorithm and prove bounds of Θ(&sqrt;n/ε + log n) and Θ(n/ε+1&sqrt;n/ε + n log n), respectively, for uniform random noise from the interval [-ε,ε]. Our results can also be applied to bound the smoothed number of points on a convex hull of points in the two-dimensional plane and to smoothed motion complexity, a concept we describe in this article. We bound how often one needs to update a data structure storing the smallest axis-aligned box enclosing a set of points moving in d-dimensional space. AU - Damerow, Valentina AU - Manthey, Bodo AU - Meyer auf der Heide, Friedhelm AU - Räcke, Harald AU - Scheideler, Christian AU - Sohler, Christian AU - Tantau, Till ID - 579 IS - 3 JF - Transactions on Algorithms TI - Smoothed analysis of left-to-right maxima with applications ER - TY - CONF AB - We present and study a new model for energy-aware and profit-oriented scheduling on a single processor.The processor features dynamic speed scaling as well as suspension to a sleep mode.Jobs arrive over time, are preemptable, and have different sizes, values, and deadlines.On the arrival of a new job, the scheduler may either accept or reject the job.Accepted jobs need a certain energy investment to be finished in time, while rejected jobs cause costs equal to their values.Here, power consumption at speed $s$ is given by $P(s)=s^{\alpha}+\beta$ and the energy investment is power integrated over time.Additionally, the scheduler may decide to suspend the processor to a sleep mode in which no energy is consumed, though awaking entails fixed transition costs $\gamma$.The objective is to minimize the total value of rejected jobs plus the total energy.Our model combines aspects from advanced energy conservation techniques (namely speed scaling and sleep states) and profit-oriented scheduling models.We show that \emph{rejection-oblivious} schedulers (whose rejection decisions are not based on former decisions) have – in contrast to the model without sleep states – an unbounded competitive ratio.It turns out that the jobs' value densities (the ratio between a job's value and its work) are crucial for the performance of such schedulers.We give an algorithm whose competitiveness nearly matches the lower bound w.r.t\text{.} the maximum value density.If the maximum value density is not too large, the competitiveness becomes $\alpha^{\alpha}+2e\alpha$.Also, we show that it suffices to restrict the value density of low-value jobs only.Using a technique from \cite{Chan:2010} we transfer our results to processors with a fixed maximum speed. AU - Cord-Landwehr, Andreas AU - Kling, Peter AU - Mallmann Trenn, Fredrik ED - Even, Guy ED - Rawitz, Dror ID - 580 T2 - Proceedings of the 1st Mediterranean Conference on Algorithms (MedAlg) TI - Slow Down & Sleep for Profit in Online Deadline Scheduling ER - TY - CONF AB - Nanoparticles are getting more and more in the focus of the scientic community since the potential for the development of very small particles interacting with each other and completing medical and other tasks is getting bigger year by year. In this work we introduce a distributed local algorithm for arranging a set of nanoparticles on the discrete plane into specic geometric shapes, for instance a rectangle. The concept of a particle we use can be seen as a simple mobile robot with the following restrictions: it can only view the state of robots it is physically connected to, is anonymous, has only a constant size memory, can only move by using other particles as an anchor point on which it pulls itself alongside, and it operates in Look-Compute-Move cycles. The main result of this work is the presentation of a random distributed local algorithm which transforms any given connected set of particles into a particular geometric shape. As an example we provide a version of this algorithm for forming a rectangle with an arbitrary predened aspect ratio. To the best of our knowledge this is the rst work that considers arrangement problems for these types of robots. AU - Drees, Maximilian AU - Hüllmann (married name: Eikel), Martina AU - Koutsopoulos, Andreas AU - Scheideler, Christian ID - 581 T2 - Proceedings of the 26th IEEE International Parallel and Distributed Processing Symposium (IPDPS) TI - Self-Organizing Particle Systems ER - TY - THES AB - Wir betrachten eine Gruppe von mobilen, autonomen Robotern in einem ebenen Gel{\"a}nde. Es gibt keine zentrale Steuerung und die Roboter m{\"u}ssen sich selbst koordinieren. Zentrale Herausforderung dabei ist, dass jeder Roboter nur seine unmittelbare Nachbarschaft sieht und auch nur mit Robotern in seiner unmittelbaren Nachbarschaft kommunizieren kann. Daraus ergeben sich viele algorithmische Fragestellungen. In dieser Arbeit wird untersucht, unter welchen Voraussetzungen die Roboter sich auf einem Punkt versammeln bzw. eine Linie zwischen zwei festen Stationen bilden k{\"o}nnen. Daf{\"u}r werden mehrere Roboter-Strategien in verschiedenen Bewegungsmodellen vorgestellt. Diese Strategien werden auf ihre Effizienz hin untersucht. Es werden obere und untere Schranken f{\"u}r die ben{\"o}tigte Anzahl Runden und die Bewegungsdistanz gezeigt. In einigen F{\"a}llen wird außerdem die ben{\"o}tigte Bewegungsdistanz mit derjenigen Bewegungsdistanz verglichen, die eine optimale globale Strategie auf der gleichen Instanz ben{\"o}tigen w{\"u}rde. So werden kompetititve Faktoren hergeleitet. AU - Kempkes, Barbara ID - 601 SN - 978-3-942647-21-2 TI - Local strategies for robot formation problems VL - 302 ER - TY - CONF AB - Dynamics in networks is caused by a variety of reasons, like nodes moving in 2D (or 3D) in multihop cellphone networks, joins and leaves in peer-to-peer networks, evolution in social networks, and many others. In order to understand such kinds of dynamics, and to design distributed algorithms that behave well under dynamics, many ways to model dynamics are introduced and analyzed w.r.t. correctness and eciency of distributed algorithms. In [16], Kuhn, Lynch, and Oshman have introduced a very general, worst case type model of dynamics: The edge set of the network may change arbitrarily from step to step, the only restriction is that it is connected at all times and the set of nodes does not change. An extended model demands that a xed connected subnetwork is maintained over each time interval of length T (T-interval dynamics). They have presented, among others, algorithms for counting the number of nodes under such general models of dynamics.In this paper, we generalize their models and algorithms by adding random edge faults, i.e., we consider fault-prone dynamic networks: We assume that an edge currently existing may fail to transmit data with some probability p. We rst observe that strong counting, i.e., each node knows the correct count and stops, is not possible in a model with random edge faults. Our main two positive results are feasibility and runtime bounds for weak counting, i.e., stopping is no longer required (but still a correct count in each node), and for strong counting with an upper bound, i.e., an upper bound N on n is known to all nodes. AU - Brandes, Philipp AU - Meyer auf der Heide, Friedhelm ID - 619 T2 - Proceedings of the 4th Workshop on Theoretical Aspects of Dynamic Distributed Systems (TADDS) TI - Distributed Computing in Fault-Prone Dynamic Networks ER - TY - CONF AB - Network creation games model the creation and usage costs of networks formed by a set of selfish peers.Each peer has the ability to change the network in a limited way, e.g., by creating or deleting incident links.In doing so, a peer can reduce its individual communication cost.Typically, these costs are modeled by the maximum or average distance in the network.We introduce a generalized version of the basic network creation game (BNCG).In the BNCG (by Alon et al., SPAA 2010), each peer may replace one of its incident links by a link to an arbitrary peer.This is done in a selfish way in order to minimize either the maximum or average distance to all other peers.That is, each peer works towards a network structure that allows himself to communicate efficiently with all other peers.However, participants of large networks are seldom interested in all peers.Rather, they want to communicate efficiently with a small subset only.Our model incorporates these (communication) interests explicitly.Given peers with interests and a communication network forming a tree, we prove several results on the structure and quality of equilibria in our model.We focus on the MAX-version, i.e., each node tries to minimize the maximum distance to nodes it is interested in, and give an upper bound of O(\sqrt(n)) for the private costs in an equilibrium of n peers.Moreover, we give an equilibrium for a circular interest graph where a node has private cost Omega(\sqrt(n)), showing that our bound is tight.This example can be extended such that we get a tight bound of Theta(\sqrt(n)) for the price of anarchy.For the case of general networks we show the price of anarchy to be Theta(n).Additionally, we prove an interesting connection between a maximum independent set in the interest graph and the private costs of the peers. AU - Cord-Landwehr, Andreas AU - Huellmann (married name: Eikel), Martina AU - Kling, Peter AU - Setzer, Alexander ID - 628 T2 - Proceedings of the 5th International Symposium on Algorithmic Game Theory (SAGT) TI - Basic Network Creation Games with Communication Interests ER - TY - CONF AB - We consider an online facility location problem where clients arrive over time and their demands have to be served by opening facilities and assigning the clients to opened facilities. When opening a facility we must choose one of K different lease types to use. A lease type k has a certain lease length lk. Opening a facility i using lease type k causes a cost of f k i and ensures that i is open for the next lk time steps. In addition to costs for opening facilities, we have to take connection costs ci j into account when assigning a client j to facility i. We develop and analyze the first online algorithm for this problem that has a time-independent competitive factor.This variant of the online facility location problem was introduced by Nagarajan and Williamson [7] and is strongly related to both the online facility problem by Meyerson [5] and the parking permit problem by Meyerson [6]. Nagarajan and Williamson gave a 3-approximation algorithm for the offline problem and an O(Klogn)-competitive algorithm for the online variant. Here, n denotes the total number of clients arriving over time. We extend their result by removing the dependency on n (and thereby on the time). In general, our algorithm is O(lmax log(lmax))-competitive. Here lmax denotes the maximum lease length. Moreover, we prove that it is O(log2(lmax))-competitive for many “natural” cases. Such cases include, for example, situations where the number of clients arriving in each time step does not vary too much, or is non-increasing, or is polynomially bounded in lmax. AU - Meyer auf der Heide, Friedhelm AU - Pietrzyk, Peter AU - Kling, Peter ID - 636 T2 - Proceedings of the 19th International Colloquium on Structural Information & Communication Complexity (SIROCCO) TI - An Algorithm for Facility Leasing ER - TY - GEN AU - Eidens, Fabian ID - 638 TI - Adaptive Verbindungsstrategien in dynamischen Suchnetzwerken ER - TY - CHAP AU - Kempkes, Barbara AU - Meyer auf der Heide, Friedhelm ID - 16445 SN - 0302-9743 T2 - Experimental Algorithms TI - Continuous Local Strategies for Robotic Formation Problems ER - TY - CONF AU - Kempkes, Barbara AU - Kling, Peter AU - Meyer auf der Heide, Friedhelm ID - 16446 SN - 9781450312134 T2 - Proceedinbgs of the 24th ACM symposium on Parallelism in algorithms and architectures - SPAA '12 TI - Optimal and competitive runtime bounds for continuous, local gathering of mobile robots ER - TY - CHAP AU - Kempkes, Barbara AU - Meyer auf der Heide, Friedhelm ID - 16448 SN - 0302-9743 T2 - Algorithms for Sensor Systems TI - Local, Self-organizing Strategies for Robotic Formation Problems ER - TY - CONF AB - We present a parallel rendering system for heterogeneous PC clusters to visualize massive models. One single, powerful visualization node is supported by a group of backend nodes with weak graphics performance. While the visualization node renders the visible objects, the backend nodes asynchronously perform visibility tests and supply the front end with visible scene objects. The visualization node stores only currently visible objects in its memory, while the scene is distributed among the backend nodes’ memory without redundancy. To efficiently compute the occlusion tests in spite of that each backend node stores only a fraction of the original geometry, we complete the scene by adding highly simplified versions of the objects stored on other nodes. We test our system with 15 backend nodes. It is able to render a ≈ 350,M polygons (≈ 8.5,GiB) large aircraft model with 20, to 30,fps and thus allows a walk-through in real-time. AU - Suess, Tim AU - Koch, Clemens AU - Jähn, Claudius AU - Fischer, Matthias AU - Meyer auf der Heide, Friedhelm ID - 16408 SN - 0302-9743 T2 - Advances in Visual Computing TI - Asynchronous Occlusion Culling on Heterogeneous PC Clusters for Distributed 3D Scenes VL - 7431 ER - TY - THES AU - Korzeniowski, Miroslaw ID - 19619 SN - 978-3-942647-08-3 TI - Dynamic Load Balancing in Peer-to-Peer Networks VL - 289 ER - TY - JOUR AU - Briest, Patrick AU - Krysta, Piotr AU - Hoefer, Martin ID - 19677 JF - Algorithmica TI - Stackelberg Network Pricing Games VL - 62 ER - TY - CONF AB - In dieser Arbeit stellen wir ein flexibles System zur Entwicklung und Evaluation von 3-D-Renderingalgorithmen vor, das die Visualisierung komplexer virtueller Szenen auf einem breiten Spektrum an Geräten erlaubt. Die Aufbereitung und Echtzeitdarstellung solcher virtueller Szenen, wie sie beispielsweise aus detaillierten CAD-Daten erzeugt werden, stellt in vielerlei Hinsicht eine algorithmische und technische Herausforderung dar. Die 3-D-Szenendaten können nach dem Dateiimport aus einem Austauschformat in eine Vielzahl unterschiedlicher Datenstrukturen überführt werden. Es muss ein geeignetes Renderingverfahren ausgewählt und eingestellt werden, welches sowohl die Eigenschaften der Szene (Zahl der Polygone, Grad der Verdeckung etc.) als auch die Fähigkeiten der Hardware berücksichtigt. Auf der einen Seite stellt die Darstellung auf mobilen Endgeräten wie Smartphones besonders hohe Anforderungen aufgrund der Speicherbeschränkung und der geringen Leistungsfähigkeit der Grafikhardware. Auf der anderen Seite stehen bei Großprojektionssystemen, wie beispielsweise dem HD-Visualisierungscenter des Heinz Nixdorf Instituts, die hohe Bildqualität bei stereoskopischer Darstellung und die Unterstützung von Trackingsystemen im Vordergrund. Der Fokus des von uns entwickelten Systems PADrend liegt in der Bereitstellung einer flexiblen und leicht erweiterbaren Grundlage für die Entwicklung und Evaluation von 3-D-Renderingalgorithmen und räumlichen Datenstrukturen im Bereich der Forschung und der universitären Ausbildung. Durch den modularen Aufbau und die große Bandbreite an unterstützten Systemen wird gewährleistet, dass eine Vielzahl unterschiedlicher Entwicklungen und Anwendungen auf PADrend aufsetzen können. In diesem Artikel geben wir einen Überblick über den Aufbau und die Fähigkeiten des Systems. Des Weiteren geben wir ein Beispiel für ein Anwendungsszenario, in dem PADrend eingesetzt wird: die Visualisierung von architektonischen Modellen auf einem Multiprojektionssystem. AU - Jähn, Claudius AU - Petring, Ralf AU - Eikel, Benjamin ID - 19845 T2 - Augmented & Virtual Reality in der Produktentstehung TI - PADrend: Platform for Algorithm Development and Rendering VL - 295 ER - TY - CONF AB - The challenging scientific field of self-reconfiguring modular robotics (i.e., decentrally controlled 'super-robots' based on autonomous, interacting robot modules with variable morphologies) calls for novel paradigms of designing robot controllers. One option is the approach of evolutionary robotics. In this approach, the challenge is to achieve high evaluation numbers with the available resources which may even affect the feasibility of this approach. Simulations are usually applied at least in a preliminary stage of research to support controller design. However, even simulations are computationally expensive which gets even more burdensome once comprehensive studies and comparisons between different controller designs and approaches have to be done. Hence, a benchmark with low computational cost is needed that still contains the typical challenges of decentral control, is comparable, and easily manageable. We propose such a benchmark and report an empirical study of its characteristics including the transition from the single-robot setting to the multi-robot setting, typical local optima, and properties of adaptive walks through the fitness landscape. AU - Hamann, Heiko AU - Schmickl, Thomas AU - Crailsheim, Karl AU - Krasnogor, Natalio AU - Luca Lanzi, Pier ID - 20180 T2 - Proceedings of the 13th Annual Genetic and Evolutionary Computation Conference, GECCO 2011 TI - Coupled inverted pendulums: A benchmark for evolving decentral controllers in modular robotics ER - TY - CONF AB - The current definitions of emergence have no effects in the context of artificial life that could convincingly be called `constructive'. They are rather descriptive labels or tests. In order to get towards recipes of generating emergence we need to know systemic characteristics that help during the design phase of artificial life systems and worlds. In this paper, we develop and discuss five hypotheses that are not meant to be irrevocable but rather thought-provoking. We introduce two modeling approaches for Langton's ant to clarify these hypotheses. Then we discuss general properties of systems, such as (ir-)reversibility, dependence on initial states, computation, discreetness, and undecidable properties of system states. AU - Hamann, Heiko AU - Schmickl, Thomas AU - Crailsheim, Karl ID - 20181 T2 - IEEE Symposium on Artificial Life (IEEE ALIFE 2011) TI - Thermodynamics of Emergence: Langton's Ant Meets Boltzmann ER - TY - CONF AU - Hamann, Heiko AU - Schmickl, Thomas AU - Crailsheim, Karl ID - 20183 SN - 0302-9743 T2 - 10th European Conference on Artificial Life (ECAL'09) TI - Evolving for Creativity: Maximizing Complexity in a Self-organized Multi-particle System VL - 5777 ER - TY - CONF AU - Hamann, Heiko AU - Schmickl, Thomas AU - Stradner, Jürgen AU - Crailsheim, Karl AU - Thenius, Rona AU - Fitch, Robert ID - 20184 T2 - Robotic Organisms: Artificial Homeostatic Hormone System and Virtual Embryogenesis as Examples TI - Robotic Organisms: Artificial Homeostatic Hormone System and Virtual Embryogenesis as Examples for Adaptive Reaction-Diffusion Controllers ER - TY - CHAP AU - Hamann, Heiko AU - Schmickl, Thomas ED - Xiao, Yang ID - 20193 T2 - Bio-inspired Computing and Communication Networks TI - {BEECLUST}: {A} Swarm Algorithm Derived from Honeybees ER - TY - CONF AU - Hamann, Heiko AU - Karsai, Istvan AU - Schmickl, Thomas AU - Stradner, Jürgen AU - Crailsheim, Karl AU - Thenius, Ronald AU - Kampis, Gyoergy AU - Szathmary, Eoers ID - 20194 T2 - Advances in Artificial Life, 10th European Conference, ECAL 2009 TI - Evolving a novel bio-inspired controller in reconfigurable robots ER - TY - CONF AU - Hamann, Heiko AU - Schmickl, Thomas AU - Crailsheim, Karl AU - Thenius, Ronald AU - Kengyel, Daniela ID - 20195 T2 - 10th European Conference on Artificial Life (ECAL'09) TI - Embodiment of Honeybee's Thermotaxis in a Mobile Robot Swarm ER - TY - CHAP AU - Hamann, Heiko AU - Schmickl, Thomas AU - Crailsheim, Karl ED - Lenaerts, Tom ED - Giacobini, Mario ED - Bersini, Hugues ED - Bourgine, Paul ED - Dorigo, Marco ED - Doursat, Rene ID - 20196 T2 - Advances in Artificial Life, ECAL 2011: Proceedings of the 11th European Conference on the Synthesis and Simulation of Living Systems TI - Explaining Emergent Behavior in a Swarm System Based on an Inversion of the Fluctuation Theorem ER - TY - CHAP AU - Hamann, Heiko AU - Schmickl, Thomas AU - Stradner, Jürgen AU - Crailsheim, Karl AU - Winkler, Lutz ID - 20214 T2 - New Horizons in Evolutionary Robotics TI - Major Feedback Loops Supporting Artificial Evolution in Multi-modular Robotics ER - TY - JOUR AU - Schmickl, Thomas AU - Hamann, Heiko AU - Crailsheim, Karl ID - 20215 IS - 3 JF - Mathematical and Computer Modelling of Dynamical Systems SN - 1387-3954 TI - Modelling a hormone-inspired controller for individual- and multi-modular robotic systems VL - 17 ER - TY - CONF AB - Occlusion culling is a common approach to accelerate real-time rendering of polygonal 3D-scenes by reducing the rendering load. Especially for large scenes, it is necessary to remove occluded objects to achieve a frame rate that provides an interactive environment. In order to benefit from the culling properly, often hierarchical data structures are used. These data structures typically create a spatial subdivision of a given scene into axis-aligned bounding boxes. These boxes can be tested quickly, but they are not very precise. By using these boxes, the included objects are detected as visible, even if other objects occlude them (false-positives). To get perfect results, the models’ original geometry included in the box has to be tested, but this would require too much computational power. To overcome this problem, original objects’ approximations could be used, but typical methods for mesh simplification cannot be applied, because they do not create an outer hull for a given object. We present a model simplification algorithm, which generates simple outer hulls, consisting of only few more triangles than a box, while preserving an object’s shape better than a corresponding bounding box. This approach is then extended to a hierarchical data structure, the so-called hull tree, that can be generated for a given scene to improve the visibility tests. Next, we present an approximative rendering algorithm, which combines the features of the hull tree with the use of inner hulls for efficient occlusion detection and global state-sorting of the visible objects. AU - Suess, Tim AU - Koch, Clemens AU - Jähn, Claudius AU - Fischer, Matthias ED - Brooks, Stephen ED - Irani, Pourang ID - 17420 T2 - Proceedings of the Graphics Interface 2011 Conference, May 25-27, St. John's, Newfoundland, Canada TI - Approximative occlusion culling using the hull tree ER - TY - CONF AU - Klaas, Alexander AU - Laroque, Christoph AU - Dangelmaier, Wilhelm AU - Fischer, Matthias ID - 17421 SN - 9781457721090 T2 - Proceedings of the 2011 Winter Simulation Conference (WSC) TI - Simulation aided, knowledge based routing for AGVs in a distribution warehouse ER - TY - CONF AU - Suess, Tim AU - Jähn, Claudius AU - Fischer, Matthias AU - Meyer auf der Heide, Friedhelm AU - Koch, Clemens ID - 17450 T2 - Augmented & Virtual Reality in der Produktentstehung TI - Ein paralleles Out-of-Core Renderingsystem für Standard-Rechnernetze VL - 295 ER - TY - THES AU - Suess, Tim ID - 17454 TI - Parallel Real-Time Rendering using Heterogeneous PC Clusters ER - TY - THES AU - Frahling, Gereon ID - 18973 SN - 978-3-942647-09-0 TI - Algorithms for Dynamic Geometric Data Streams VL - 290 ER - TY - THES AU - Mehler, Jan ID - 18974 SN - 978-3-942647-06-9 TI - Power-Aware Online File Allocation in Dynamic Networks VL - 287 ER - TY - THES AB - Web computing is a variant of parallel computing where the idle times of PCs donated by worldwide distributed users are employed to execute parallel programs. In this thesis we consider a web computing variant with two important properties: First, we support the execution of coupled, massively parallel algorithms (rather than distributed data processing). And second, we organize the system in peer-to-peer fashion. We present the Paderborn University BSP-based Web Computing (PUB-Web) library, which supports the execution of parallel programs in the bulk-synchronous style (BSP) in such a web computing setting. In this thesis, we focus on important technical and algorithmic aspects, in particular: In order to schedule processes with respect to the currently available computing power, which continually changes in an unpredictable fashion, we need intelligent load balancing algorithms and -- as a basic precondition -- the technical ability to migrate threads at runtime. To achieve the latter in a way suitable for production use, compatible with recent Java versions, available for all important platforms, and easy-to-use for developers, we develop the PadMig thread migration and checkpointing library. In order to tackle the distributed load balancing problem, we present an algorithm based on Distributed Heterogeneous Hash-Tables. In order to judge the quality of the schedules produced, we perform extensive experiments to compare several variants of the DHHT-based load balancer with the well- established Work Stealing algorithm, using realistic input data obtained by profiling the utilization of several hundred PCs for a period of several months. Beside the available computing power, we finally also consider the network bandwidth as a secondary criterion for load balancing. For this purpose, we cluster the PUB-Web network according to bandwidth, employing a novel, fault-tolerant, adaptive, and scaling distributed clustering algorithm called DiDiC. In order to judge the quality of the clusterings produces by DiDiC, we experimentally compare it to the well-established MCL algorithm using a simulator. AU - Gehweiler, Joachim ID - 18976 SN - 978-3-942647-17-5 TI - Peer-to-Peer Based Parallel Web Computing VL - 298 ER - TY - CONF AU - Briest, Patrick AU - Raupach, Christoph ID - 19026 SN - 9781450307437 T2 - Proceedings of the 23rd ACM symposium on Parallelism in algorithms and architectures - SPAA '11 TI - The car sharing problem ER - TY - THES AU - Effert, Sascha ID - 19040 TI - Verfahren zur redundanten Datenplatzierung in skalierbaren Speichersystemen ER - TY - JOUR AB - This paper deals with the design of efficiently computable incentive-compatible mechanisms for combinatorial optimization problems with single-minded agents each possibly having multiple private parameters. We focus on approximation algorithms for NP-hard mechanism design problems. These algorithms need to satisfy certain monotonicity properties to ensure truthfulness. Since most of the known approximation techniques do not fulfill these properties, we study alternative techniques. Our first contribution is a quite general method to transform a pseudopolynomial algorithm into a monotone fully polynomial time approximation scheme (FPTAS). This can be applied to various problems like, e.g., knapsack, constrained shortest path, or job scheduling with deadlines. For example, the monotone FPTAS for the knapsack problem gives a very efficient, truthful mechanism for single-minded multiunit auctions. The best previous result for such auctions was a 2-appro-xi-ma-tion. In addition, we present a monotone PTAS for the generalized assignment problem with any constant number of private parameters per agent. The most efficient way to solve packing integer programs (PIPs) is linear programming–based randomized rounding, which also is in general not monotone. We show that primal-dual greedy algorithms achieve almost the same approximation ratios for PIPs as randomized rounding. The advantage is that these algorithms are inherently monotone. This way, we can significantly improve the approximation ratios of truthful mechanisms for various fundamental mechanism design problems like single-minded combinatorial auctions (CAs), unsplittable flow routing, and multicast routing. Our primal-dual approximation algorithms can also be used for the winner determination in CAs with general bidders specifying their bids through an oracle. AU - Briest, Patrick AU - Krysta, Piotr AU - Vöcking, Berthold ID - 23739 JF - SIAM Journal on Computing SN - 0097-5397 TI - Approximation Techniques for Utilitarian Mechanism Design ER - TY - JOUR AB - We investigate nonparametric multiproduct pricing problems, in which we want to find revenue maximizing prices for products $\mathcal{P}$ based on a set of customer samples $\mathcal{C}$. We mostly focus on the unit-demand case, in which products constitute strict substitutes and each customer aims to purchase a single product. In this setting a customer sample consists of a number of nonzero values for different products and possibly an additional product ranking. Once prices are fixed, each customer chooses to buy one of the products she can afford based on some predefined selection rule. We distinguish between the min-buying, max-buying, and rank-buying models. Some of our results also extend to single-minded pricing, in which case products are strict complements and every customer seeks to buy a single set of products, which she purchases if the sum of prices is below her valuation for that set. For the min-buying model we show that the revenue maximization problem is not approximable within factor $\mathcal{O}(\log^{\varepsilon}|\mathcal{C}|)$ for some constant $\varepsilon>0$, unless $\mathrm{NP}\subseteq\mathrm{DTIME}(n^{\mathcal{O}(\log\log n)})$, thereby almost closing the gap between the known algorithmic results and previous lower bounds. We also prove inapproximability within $\mathcal{O}(\ell^{\varepsilon})$, $\ell$ being an upper bound on the number of nonzero values per customer, and $\mathcal{O}(|\mathcal{P}|^{\varepsilon})$ under slightly stronger assumptions and provide matching upper bounds. Surprisingly, these hardness results hold even if a price ladder constraint, i.e., a predefined order on the prices of all products, is given. Without the price ladder constraint we obtain similar hardness results for the special case of uniform valuations, i.e., the case that every customer has identical values for all the products she is interested in, assuming specific hardness of the balanced bipartite independent set problem in constant degree graphs or hardness of refuting random 3CNF formulas. Introducing a slightly more general problem definition in which customers are given as an explicit probability distribution, we obtain inapproximability within $\mathcal{O}(|\mathcal{P}|^{\varepsilon})$ assuming $\mathrm{NP}\nsubseteq\bigcap_{\delta>0}\mathrm{BPTIME}(2^{\mathcal{O}(n^{\delta})})$. These results apply to single-minded pricing as well. For the max-buying model a polynomial-time approximation scheme exists if a price ladder is given. We give a matching lower bound by proving strong NP-hardness. Assuming limited product supply, we analyze a generic local search algorithm and prove that it is 2-approximate. Finally, we discuss implications for the rank-buying model. AU - Briest, Patrick AU - Krysta, Piotr ID - 23740 JF - SIAM Journal on Computing SN - 0097-5397 TI - Buying Cheap Is Expensive: Approximability of Combinatorial Pricing Problems ER - TY - CHAP AU - Cord-Landwehr, Andreas AU - Degener, Bastian AU - Fischer, Matthias AU - Hüllmann, Martina AU - Kempkes, Barbara AU - Klaas, Alexander AU - Kling, Peter AU - Kurras, Sven AU - Märtens, Marcus AU - auf der Heide, Friedhelm Meyer AU - Raupach, Christoph AU - Swierkot, Kamil AU - Warner, Daniel AU - Weddemann, Christoph AU - Wonisch, Daniel ID - 20709 SN - 0302-9743 T2 - SOFSEM 2011: Theory and Practice of Computer Science TI - Collisionless Gathering of Robots with an Extent ER - TY - CHAP AU - Cord-Landwehr, Andreas AU - Degener, Bastian AU - Fischer, Matthias AU - Hüllmann, Martina AU - Kempkes, Barbara AU - Klaas, Alexander AU - Kling, Peter AU - Kurras, Sven AU - Märtens, Marcus AU - Meyer auf der Heide, Friedhelm AU - Raupach, Christoph AU - Swierkot, Kamil AU - Warner, Daniel AU - Weddemann, Christoph AU - Wonisch, Daniel ID - 20710 SN - 0302-9743 T2 - Automata, Languages and Programming TI - A New Approach for Analyzing Convergence Algorithms for Mobile Robots ER - TY - CONF AU - Renken, Hendrik AU - Laroque, Christoph AU - Fischer, Matthias ID - 18193 T2 - Proceedings of The 25th European Simulation and Modelling Conference - ESM2011 TI - An Easy Extendable Modeling Framework for Discrete Event Simulation Models and their Visualization ER - TY - GEN AB - We present a parallel rendering system for PC-Clusters to visualize large 3D scenes. One single visualization node, equipped with a high-end graphics adapter, is supported by a group of backend nodes with weak graphics performance. The objects of the scene are distributed among these backend nodes, they serve two purposes: First, they provide an out-of-core memory system for the visualization node. Second, they assist the visualization node's rendering by performing visibility calculations and only sending visible objects to the visualization node. In order to obtain fast rendering with our system, we have to distribute the objects among the backend nodes in a way that does not only guarantee an even distribution of the objects, but also an even distribution of the visibility calculations and the amount of data send to the visualization node. We identify necessary properties of the distribution and argue that a random distribution is a good candidate. Further, in order to reduce the number of objects sent to the visualization node per frame, we employ an approximate hierarchical occlusion culling in each backend node. For this, they are equipped, in addition to the objects assigned to them, with simplified versions of the other objects of the 3D scene. The visualization node is equipped with 512 MiB video memory and supported by 15 backend nodes. This system is able to render a approx. 350 million polygons (approx. 8.5 GiB) large aircraft model between 20 - 30 fps and thus allows a walkthrough in real-time. AU - Suess, Tim AU - Koch, Clemens AU - Jähn, Claudius AU - Fischer, Matthias AU - Meyer auf der Heide, Friedhelm ID - 18194 TI - Parallel Out-of-Core Occlusion Culling ER - TY - CONF AU - Vöcking, Berthold AU - Hoefer, Martin AU - Skopalik, Alexander AU - Penn, Michal AU - Polukarov, Maria ID - 18568 T2 - {IJCAI} 2011, Proceedings of the 22nd International Joint Conference on Artificial Intelligence, TI - Considerate Equilibrium ER -